1. Field of the Invention
The present invention generally relates to providing power to one or more networked devices via network cabling. More particularly, the present invention relates to providing power to one or more networked devices in one of at least two modes: a low power mode and a high power mode.
2. Description of the Background Art
Recently, there has been considerable effort to develop mechanisms to deliver DC power over the same cable used for Ethernet data transmission. As part of this “Power over Ethernet” (POE) effort, the industry has focused on low power applications that require less than 13 watts of DC power, operate within the safe electrical low voltage (SELV) region, and are powered using a single Class 2 power supply. Among other National Electric Code requirements, a Class 2 circuit includes a power-limited supply having a rating of less than 100VA, for dry indoor use in non-hazardous locations.
As part of the industry effort to develop POE, an IEEE 802 Working Group, IEEE802.3af is developing a specification for delivering POE for low power applications. The specification defines the functional and electrical characteristics for two devices: a power source and a powered device. The power supplied is 48 volts nominal, 13 watts, and is delivered using two of four twisted-wire pairs of a twisted pair cable (e.g., a Category 5 or Category 6 cable).
The current POE work falls short of meeting requirements that make it applicable to a wider range of applications. Specifically, the power specification of 13 watts is far too restrictive. On one hand, devices that need less than 13 watts will need to be powered by a power source that can deliver 13 watts (instead of a power source that can be designed to deliver less power). On the other hand, a powered device that needs more than 13 watts cannot be powered by existing POE solutions.